DESCRIPTION: (from the applicant's abstract) Most neurons of the adult central nervous system are terminally differentiated, exist through the life of the organism and, when they die, are not replaced. However, evidence exists that small populations of neurons continue to be born in the adult ventricular zone and hippocampus. Given adult hippocampal granule cells continue to be born through the life of the rodent and FGF-2 can induce hippocampal neuroblast proliferation in vitro , we designed a set of experiments to determine if adult hippocampal cells could be isolated and expanded in vitro to an adequate number for transplantation back into the adult hippocampus. Our results show that cells of the adult nervous system can be isolated and characterized, expanded indefinitely in vitro , genetically labeled in vitro , and transplanted back into the adult central nervous system where they can survive and differentiate in a target-specific manner into neurons. In this grant we plan to extend these observations by conducting the following experiments. 1) We will isolate individual cells of the expanded population of the progenitor cells and grow them as clones to determine the pluripotentiality of the progeny of each of the clones. We will define conditions that influence the fate of the progenitor cells toward glial or neuronal lineage. 2) We will determine if, and to what extent, adult progenitors survive engraftment to the developing and adult brain. We will then determine whether the grafted cells will differentiate and which phenotypic markers they express at different time points following implantation. Finally in this aim we will determine exogenous and endogenous factors that influence the extent of cell survival and the fate of cells following grafting. 3) We will implant the cells into the damaged CNS to determine if they can participate in the repair process, or replace missing cells. Independently of our success in the preceding component of this aim we will genetically engineer the progenitor cells to make and secrete the product, then implant the cells into a relevant animal model. Finally in this aim we will inject FGF-2 chronically in the adult brain to induce proliferation and differentiation of the endogenous progenitor cells.